package day_2022_4_to_7.day48;

import java.util.Scanner;

/**
 * 客似云来
 * @author haomin
 * @date 2022/06/01 18:13
 **/

public class Day33_2_TwoFib {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        while(in.hasNext()){
            int start = in.nextInt();
            int end = in.nextInt();

            long[] dp = new long[end + 2];
            long result = 0;
            dp[1] = 1;
            dp[2] = 1;
            for(int i = 3;i < end+1;i++){
                dp[i] = dp[i-1] + dp[i-2];
            }

            for (int i = start; i <= end ; i++) {
                result += dp[i];
            }
            System.out.println(result);
        }
        in.close();
    }
}